Gas burner and mixing tube construction



June 6, 1950 N. E. HILL ET AL GAS BURNER AND MIXING TUBE CONSTRUCTIONFiled April 4, 1946 Q ENAAQNA F Patented June 6, 1950 GAS BURNER ANDMIXING TUBE CONSTRUCTION Napoleon E. Hill, Otto J. Bess, and Erank J.

Nunlist, Jr., Milwaukee, Wis assignors to, L. J. Mueller Furnace CompanyApplication April 4;. 1946;8erlal Nm' 65956.29

3 Claims. 1

This invention relates to improvements in gas burner and mixing tubeconstructions.

A general objectof the. invention is to. provide an improved gas burnerand mixing tube so constructed as to eliminate extinction noise andflashback characteristics.

In connection with the operation otgas burners having conventionalmixing tubes associatedtherewith, considerable difliculty has beenexperienced when burning gas-with high ignition velocitycharacteristics. Avery pronounced objection has been the extinctionnoise and flashback characteristics common to the operation of gasburners formedwithconventional mixing tubes. It is the theory that insuch structures the extinction noise and flashback characteristics arecaused by the following conditions: When the supply of, gas. to theburner isshut 011', there is, of course, residual gas. in the pipingbetween the shut-off valve and the burner ports or orifices; Upon theclosing of .the gas supply shut-off valve, the quantity of gas Withinthe device and reaching the burner ports isgradually reduced.Consequently, there is less energy in the gas streams leaving the burnerports and the quantity of primary air within the'mechanism isconsequently reduced. However, the ratio of primary air togas greatlyincreases. Up toa definite ratio of primary air to: gas, the ignitionvelocity of the combustible mixture increases and a situation attainswherein after the .gas supply shut-cif valveto the. mixing tube isclosed, the ignition velocity increases until it is greater than thevelocity of the primary air-gas mixture in the burner ports. At suchtime the flame will travel back or recede through the burner ports intothe burner head and will ignite the primary air-gas mixture therein. Ifthere is a sufficient volume of the combustible mixture within the.mechanism, an explosion or extinction noiseresults.

With the foregoing explanation in mind, the present invention aims ateliminating objectionableexplosions and extinction noises inherent tothe operation of conventional gas burner mech: anisms by providing a.gas burner and mixing tube construction wherein the mixing tubecommunicating with the burner head has associated therewith a trap whichextends above the level of the burner ports. Inasmuch as theair-gas.mixture within the burner head has a specific gravity less than that ofair, with the improved elevated trap construction associated with themixing tube, after the gas supply valve has been shut oif, the air-gasmixturein the burner head a tends to fiow into, and rise to the highestpoint in the trani, Such trapped air-gasmixture within the trap thentends to block or counteract the-normalfiowof air admitted through anair valveina lower portionof the trapiandby blocking the flowofadditional air, the flashback, orflextinction noise tendency of the.burneris overcome.

Camel-e specific object of the invention is to providers gas-burner andmixing, tube. construetion wherein the mixing tube, remote from theburner head, carriesan elevated cylindrical trap whichhasl-located'therein below its top, air-and gas inlets.

-A further object'of the .inventionis to providee'gas burner and mixingtubeconstruction wherein thewmixingtube has aportion of substantiallengthat an elevation. above the; elevation'of the burnergas ports, andwhich terminates, remote from the burner, in a trap of relativelylargevolume and projecting above the level of the. burner gas ports,said elevated portions ofthe mixing tube and trap being adapted toreceive a light air-gas mixture-and to hold the same, under certainconditions, as a curtain between the primary air :andgas inlets and theburner ports.

A further object of the invention is to providea gas burner and.mixingtube construction of such iormationthat the primary airand/or theprimary air-gas mixture must travel upwardly and then: downwardly beforereachingthe burner head with the uppermost v ointof flow beingsubstantially abovethe planeof the burner ports.

'A further object of'the invention is. to providea gasburner andmixingtube construction which is very simplais'easy to install, service andreg-- ulate, is relatively inexpensive, which functions eflieiently,andwhich is well adapted for the purposes. described.

'With. the above and'other objects inview, the invention consists of theimproved gas burner and mixing tube constructiomand its parts andcombinations as set forth in the claims, and all equivalents thereof.

In the. accompanying drawing in which the samexreference charactersindicate the same partsin all of the views:

Fig. 1 isaside view,.partlyin longitudinal ver- 'tical sectional viewofthe improved'gas burner andzmixing tube construction with an outer endportiongofthe burner head being broken away;

Fig. 2 is a plan viewof the gas burner and mixing tube; and

Fig.3 is a fragmentary inverted plan view oi 3 that portion of theapparatus which includes the mixing tube and trap.

Referring now more particularly to the drawing, it will be observed thata hollow gas burner is indicated generally by the numeral 8. The burnerhead may be of any desired accepted shape and may take the form of a T,as illustrated. In top wall portions of the burner head there are aplurality of burner port stools 9 with drilled gas ports or orifices ltherethrough. The particular type of gas port referred to is merely byway of illustration and the burner head may, within the purport of theinvention, be formed with any conventional type of gas port. The innerend of the burner head 8 is curved upwardly and the gas entrance endtherein is surrounded by an annular shoulder I2 adapted to have seatedthereon the adjacent end of a mixing tube, indicated generally by thenumeral IS. The end portion of the mixing tube referred to is securelyconnected to the shoulder l2 of the burner head by any suitable meanswhich will provide a gas tight joint.

The mixing tube I3 is venturi-like in formation with the end adjacentthe burner head being enlarged and curved downwardly to engage theupturned end of the burner head. The major extent of the mixing tube ishorizontal and the same extends at an elevation substantially above theplane of the burner ports H1. The composite structure which includes theburner head 8 and the mixing tube I3 is of goose neck formation.

The outer reduced end' of the mixing tube l3 has formed integraltherewith a cylindrical 'casing l4 whose longest dimension is in avertical plane. The closed upper end of the casing I4 is disposedsomewhat above the mixing tube IS. The hollow interior of the casing l4therefore provides a trap for the purpose hereinafter to be explained,with the interior of the casing having an outlet to the mixing tubesomewhat below the top of the casing.

On the side wall of the casing l4 opposite the connection of the casingwith the end of the mixing tube i3 is an apertured boss l5 havin securedtherethrough a gas supply nipple l6 which is in connection with anoutwardly extending gas supply pipe H. The discharge end of the gasnipple i6 is so arranged relative to the casing I 4 that it dischargesthereinto generally in alinement with the outer end of the mixing tubeI3 and the axis of said mixing tube.

The lower open end of the cylindrical casing I4 is provided with spacedradial webs l 8 adapted to cooperate with an air shutter l9, said webshaving a central boss 20 to which is attached by means of a bolt 2|, theadjustable air shutter l9, previously referred to. The adjustable airshutter I9 is of the type which may be turned circularly to more or lessclose or open the spaces between the fixed webs l8 for the purpose ofcontrolling the amount of primary air admitted into the trap formingcasing 14.

Depended from a transverse portion of the burner head 8 is a tappedflange 22 which may be used for the attachment of pilot light equipment.From Fig. 1 it will be observed that the mixing tube [3 provides a gascarrying conduit which is above the level of the burner ports [0.Likewise, the major portion of the interior of the casing I4 is abovethe level of the burner ports. The gas supply nipple I5 is arranged tosupply gas into the apparatus in a stream which is directed toward theopen end of the mixing tube I3 and co-axially with said mixing-tube.

The point of introduction of the gas is at an elevation above the planeof the burner ports In. On the other hand, the primary air enters theinterior of the casing ID at a considerably lower elevation and thedirection of flow of incoming primary air is at right angles to thedirection of flow of incoming gas.

If, as is conventional in the operation of a gas burner, an automaticshutofi valve (not shown) terminates gas flow from the gas supply pipel1 and nipple l6 into the casing II, a condition will thereafter existwhere only primary air enters the casing l4 and flows into the mixingtube l3. The air-gas mixture within the apparatus will obviously becomediluted. For a time this residual combustible mixture within theapparatus will flow into the hollow burner head 8 and will exhaustthrough the burner ports I!) where combustion takes place. Eventually, acondition will develop wherein the ignition velocity becomes greaterthan the velocity of the air-gas mixture at the burner ports. Thisinduces a condition wherein there would ordinarily be a tendency for theflame to travel back into the burner head and ignite the air-gas mixturetherein, resulting in a flashback or extinction noise. The presentimprovements prevent this highly objectionable contingency because theairgas mixture in the burner head, being lighter than air, will tend toflow back through the burner head and rise into the elevated portions ofthe mixing tube I3 and easing [4, said portions being above the plane ofthe burner ports. Consequently, this arrangement serves to establish acurtain of light air-gas mixture within said elevated portions of theapparatus. This light air-gas mixture curtain is interposed between theprimary air inlet in the lower end of the casing l4 and the gas ports [0and thereby serves to block the normal flow of primary air whichcontinues to enter the casing Ill, preventing the incoming primary airfrom further diluting the residual combustible gas in that portion ofthe apparatus adjacent which the ignition occurs, preventing flashbacksand extinction noises.

It is to be noted that the casing M at the outer end of the mixing tubel3 provides a relatively large capacity, trap or reservoir and undernormal conditions it enhances the admission of primary air and gas whichare admitted at spaced points and in a manner so that the respectivestream are generally at right angles to each other.

From the foregoing description, it will appear that the improved gasburner and mixing tube construction is both simple and novel, eliminatesobjections inherent to conventional gas burner and mixing tubeconstructions, and is well adapted for the purposes described.

What we claim as our invention is:

l. A composite gas burner head and mixing tube assembly of goose neckformation wherein the mixing tube portion extends horizontally at anelevation substantially above the burner head portion, the latter beingparallel to the major extent of the mixing tube and being provided withburner ports in the top portion thereof, a hollow casing entered by theouter end of the mixing tube portion and extending above the planes ofthe mixing tube and burner head portions, and spaced apart meansentering right angularly sep arated'wall portions of the casing foradmitting primary air and gas in a manner so that the primary air streamenters said casing at substantially right angles to the entering gasstream.

2. In a gas burner construction, a hollow elongated burner head formedwith upwardly opening burner ports in the top portion thereof, a mixingtube having an elongated rectilinear portion and an elbow portion, thelatter portion being connected to the burner head so as to open into theinterior of the latter at substantially a right angle to the axial lineof the burner head and disposing the rectilinear portion of the mixingtube at an elevation above the plane of the burner ports, a hollowcasing carried by the outer end of the rectilinear portion of the mixingtube and communicating therewith and having a portion extendedsubstantially above said rectilinear portion and above the plane of theburner ports, means for admitting primary air into said casing below theaxial line of the mixing tube, and means for admitting gas into saidcasing at a point above the line of the burner ports, whereby thegas-air mixture must flow through the elevated mixing tube and thendownwardly through the elbow portion thereof and then longitudinallythrough the burner head before being upwardly exhausted through theburner ports.

3. In a gas burner construction, a hollow, elongated, horizontallydisposed burner head formed with upwardly opening burner ports in thetop portion thereof, a mixing tube having an elongated rectilinearportion and an elbow portion, the latter being connected to and incommunication with the burner head and disposing the rectilinear portionof the mixing tube parallel with and above the burner head, the outerend portion of the mixing tube being enlarged to form a chamber whichdepends below the axial line of the rectilinear portion of the mixingtube, means for admitting primary air into a lower portion of saidchamber, and means for admitting gas into a higher portion of saidchamber, the arrangement being such that the gas-air mixture flowsthrough the elevated mixing tube and then downwardly and into the burnerhead for discharge in an upward direction through the burner ports.

NAPOLEON E. HILL.

OTTO J. RESS.

FRANK J. NUNLIST, JR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 700,020 Dennis May 13, 19021,080,600 Spahr Dec. 9, 1913 FOREIGN PATENTS Number Country Date 239,256Great Britain Sept. 2, 1925

